For August, Yosemite powered 3.3% of all Macs, according to metrics vendor Net Applications. That was 33 times the user share of its predecessor, OS X Mavericks, in September 2013, one month before its official launch, and nearly one-third of Mavericks' share the following month, when it was first made available to all customers.

The 3.3% represented a large number of Macs: With approximately 80 million Macs in use -- a figure recently touted by Apple -- the Net Applications stat meant about 2.6 million machines ran the unreleased operating system last month.

The biggest difference between this year and last for Apple's OS X rollout was that the company let anyone running Mavericks upgrade to a public preview of Yosemite starting July 24.

(Net Applications listed Yosemite as "OS X 10.1" in its stats, but the company's head of marketing, Vince Vizzaccaro, confirmed that a "0" had been dropped. The item was, in fact, Yosemite.)

By Net Applications' count, Yosemite has grown much more rapidly in its prerelease time frame than Mavericks did, even before the public beta -- Apple's first since 2000 -- opened the gates to more users.

Net Applications pegged Yosemite's share of all Macs at 0.9% in June and at 1.2% in July. Last year, the analytics company did not list the preview of Mavericks until September, when that edition accounted for just 0.1% of all Macs.

So even before the launch of the public beta, Yosemite was on a larger percentage of Macs than its forerunner, Mavericks, had been in the summer of 2013. The increased developer interest could be attributed to the partial visual refresh Apple did on the operating system and the tighter integration with the also-upcoming iOS 8. The cornerstone of that integration is Handoff, part of "Continuity," a term Apple has used to describe several features of iOS and OS X that allow users to start an activity -- writing an email, browsing the Web, creating a document -- on one device and then put it aside and later resume it on another device.

The gains by Yosemite came from Mavericks, the required starting point for trying either the developer or public previews. That, in turn, has suppressed Mavericks' growth -- in August it gained just half the user share average of the preceding six months.

Mavericks was once projected to reach a 72% user share by the time Yosemite arrived, but that target will not be reached because of the public beta and greater interest by developers. Computerworld now forecasts Mavericks will top out at around 67% next month, then take a big hit in October when users begin upgrading to Yosemite.

Apple has not named a ship date for Yosemite, but if it follows 2013's timetable, the most likely date is Oct. 22.

Data: Net Applications

Apple's OS X Yosemite has grabbed a 3% share of all Macs two months before its official release, thanks to the company's first public beta in 14 years.